1. Field of the Invention
The present invention relates to a waveguide coupler of waveguide terminals formed in dielectric substrates used in conjunction with a high frequency band, such as microwave or millimeter-wave band.
2. Description of the Related Art
FIG. 1 is an exploded perspective view showing a configuration for coupling waveguide terminals formed in dielectric substrates by a conventional waveguide coupler. FIG. 2 is a side view when the waveguide terminals are joined together by a conventional waveguide coupler. In FIGS. 1 and 2, 1a and 1b indicate dielectric substrates, 2a, 2b (see FIG. 2), 2c, 2d, and 2e (see FIG. 2) indicate waveguide terminals, 3a and 3b indicate carriers, 4 indicates a waveguide adapter, 5 indicates a screw hole formed in the waveguide adapter, and 6 (see FIG. 2) indicates a screw.
An example of such a conventional waveguide coupler will be described. In FIGS. 1 and 2, the dielectric substrates 1a and 1b having the waveguide terminals 2a and 2e formed therein are bonded to the carriers 3a and 3b, respectively, having the waveguide terminals 2b and 2d with an adhesive or by soldering or brazing. The two dielectric substrates bonded to the carriers are aligned with the waveguide adapter 4 so that the positions of the waveguide terminals 2b, 2c, and 2d coincide with each other, and then fastened at the screw holes 5 with the screws 6. Thus, the conventional dielectric substrates having the waveguide terminals formed therein are connected together with screws via carriers, a waveguide adapter, and so on.
A transmitter-receiver circuit, for example, is provided on the dielectric substrates 1a, 1b, for converting high frequency radio waves transmitted through a waveguide to electrical signals transmitting through a conductor, and vice versa. The transmitter circuit generates a high frequency signal in response to a signal entered externally to the dielectric substrate and supplies it to the carriers 3a, 3b side from the waveguide terminals 2a, 2e. On the other hand, the receiver circuit converts the high frequency signal entered from the carriers 3a, 3b side to the waveguide terminals 2a, 2b to an electrical signal and supplies it externally, for example.
As described above, because conventional waveguide couplers use expensive carriers and waveguide adapter and are fastened with screws, efforts to reduce their cost have failed, and they continue to suffer from degraded machinability. Moreover, because the carriers and the waveguide adapter generally have different coefficients of thermal expansion, when the dielectric substrates are connected and fixed on the carriers and the waveguide adapter using an adhesive, there is a risk of ablation of the adhesive surface or fracture of associated members. Further, the wiring for input/output of electrical signals to/from the circuit on the dielectric substrate is formed by connecting wire materials onto the top surface of the dielectric substrate by bonding, for example, which complicates the manufacturing process.